The largest potential problem facing Tent users is that of condensation build up.  This occurs when the occupants are within the Tent, and as they breathe and perspire, they generate moisture vapour.
This moisture will circulate within the inner tent, and due to the nature of this fabric, the moisture is allowed to pass through it.  The moisture will then come into contact with the inside edge of the flysheet.  At night when the temperature drops rapidly, the flysheet will become cold.  When the warm moisture vapour comes into contact with the flysheet it cannot escape to the outside edge for evaporation (as the flysheet itself is not breathable)…  This is where condensation forms.

Cone ventilators are fitted to the flysheet, to allow the moisture to evaporate.  A large number of dome tents are also fitted with a mesh “chimney” on the top for extra ventilation.  Condensation may give the impression that the tent is leaking – this is fairly unlikely if the seams have been sealed and the nylon treated

Separation.

In a dome, tunnel or geodesic Tent, there will be an air gap between the inner tent and the flysheet. This is there to prevent any condensation coming back through the inner tent. There must be a seperation between inner and flysheet when pitching.